System and method for monitoring pre-eclamptic patients

ABSTRACT

A system and method for monitoring and estimating the blood pressure of a pregnant patient that modifies the blood pressure estimating algorithm when the patient is pre-eclamptic. The level of carbon monoxide within a patient&#39;s bloodstream or exhaled breath can be analyzed to determine whether a pregnant patient is pre-eclamptic. After the patient has been diagnosed as pre-eclamptic, the NIBP monitoring system adjusts its algorithm for estimating the patient&#39;s blood pressure to compensate for the physical changes that occur in the patient during pre-eclampsia. The adjusted blood pressure estimates calculated by the NIBP monitoring system can be calculated using different adjustment techniques and methods and are displayed on the NIBP monitor.

BACKGROUND OF THE INVENTION

The present invention relates to an automated blood pressure measuringapparatus and method. More specifically, the present invention relatesto an automated, non-invasive blood pressure (NIBP) monitor thatincludes optimized operation for use with pregnant patients,particularly those that are diagnosed as pre-eclamptic, to provide moreaccurate measurements of the patient's blood pressure.

Automated blood pressure monitoring has rapidly become an accepted and,in many cases, essential aspect of patient care. Such automated monitorsare now a conventional part of the patient environment in emergencyrooms, intensive and critical care units, and in fetal monitoringsystems.

The oscillometric method of measuring blood pressure involves applyingan inflatable cuff around an extremity of the patient's body, such asthe patient's upper arm. The cuff is inflated to a pressure above thepatient's systolic pressure and the cuff pressure is then reduced eithercontinuously or incrementally in a series of small steps. A pressuretransducer in communication with the blood pressure cuff measures thecuff pressure, including pressure fluctuations resulting from thebeat-to-beat pressure change in the artery under the blood pressurecuff. The data obtained from the pressure transducer is used by aprocessor within the NIBP monitor to compute the patient's systolicpressure, mean arterial pressure (MAP) and the diastolic pressure.

An example of the oscillometric method of measuring blood pressure isshown and described in U.S. Pat. Nos. 4,360,029; 4,394,034; and4,638,810, which are commonly assigned with the present invention.

Although NIBP monitors and methods, such as the oscillometric methoddescribed above, are effective in determining the blood pressure of apatient, the algorithms used within the processor of the NIBP monitoroften provide marginally lower measurements for the blood pressurewithin high-risk obstetric patients, such as those suffering frompregnancy-induced hypertension and pre-eclampsia. Pregnancy-inducedhypertension is hypertension that develops as a consequence of pregnancyand regresses after delivery. Pre-eclampsia is a type ofpregnancy-induced hypertension characterized by progressive hypertensionand pathological edema.

During pre-eclampsia, the physical characteristics of a patient'svascular system change, which can affect the accuracy of an NIBPmonitoring algorithm that was tested in normotensive pregnant patients.As an example, the normal algorithm used to estimate both the systolicand diastolic blood pressure in a patient being monitored by an NIBPsystem calculates the systolic and diastolic pressures based upon aratio from the determined mean arterial pressure (MAP). In an obstetricpatient suffering from pre-eclampsia, these ratios used to estimate thesystolic and diastolic blood pressure in an NIBP monitor tend to resultin blood pressure measurements that are slightly lower than the manualblood pressure measurements taken by a physician utilizing a bloodpressure cuff and a stethoscope. Since physicians are accustomed totreating patients based upon the manual blood pressure measurementstaken using a blood pressure cuff and stethoscope, the underestimationof both the systolic and diastolic pressure when utilizing an automatedNIBP monitoring system may not indicate the onset of pre-eclampsia atthe same stage as would have been determined utilizing the manual bloodpressure cuff and stethoscope determination technique.

Recently, studies have determined that the end tidal carbon monoxide(etCO) levels in pregnant women are lower when the women havegestational hypertension and/or pre-eclampsia as compared to anormotensive pregnant patient. Kreiser, D et al End tidal carbonmonoxide levels are lower in women with gestational hypertension andpre-eclampsia. J Perinatol, Apr. 1, 2004; 24(4): 213-7. As an example,the etCO values in women suffering from pre-eclampsia were less than orequal 1.6 ppm in 89% of the patients suffering from pre-eclampsia ascompared with only 45%, 54% and 46% of non-pregnant, first and thirdtrimester normotensive pregnant women. Thus, the results of the studyindicate that the etCO levels in women with gestational hypertension orpre-eclampsia were significantly lower than normotensive pregnant women.Thus, the low levels of carbon monoxide in pregnant women is believed tobe an indication of pregnancy-induced hypertension and pre-eclampsia,which can be utilized in addition to a typical blood pressuremeasurement for a clinician in diagnosing the disorder.

SUMMARY OF THE INVENTION

The following describes a method and system for determining the bloodpressure of a patient that has been diagnosed as pre-eclamptic.Preferably, the system includes a non-invasive blood pressure (NIBP)monitoring system as well as a carbon monoxide detection device thatprovides an indication of the level of carbon monoxide within thepatient's expired breath or bloodstream in real time.

The carbon monoxide detection device is operable to determine the carbonmonoxide level present within the patient in real time. In onecontemplated embodiment, the carbon monoxide detection device is a pulseoximeter sensor modified to determine the level of carboxyhemoglobin(COHb) within the patient's bloodstream. Based upon the level of COHbwithin the patient's bloodstream, either the carbon monoxide detectiondevice or the processor of the NIBP monitoring system can determinewhether the pregnant patient is pre-eclamptic.

Alternatively, the carbon monoxide detection device can be a gas sensingdevice that determines the end tidal breath CO (etCO) level within theexpired breath of the patient. The carbon monoxide detection device caneither perform the analysis to determine pre-eclamptic conditions or theprocessor of the NIBP system can receive the etCO level and determinewhether the patient is pre-eclamptic.

Further, the NIBP monitoring system can receive an indication ofpre-eclampsia from a remote electronic medical records database thatincludes other test results that indicate the patient is pre-eclamptic.The pre-eclamptic diagnosis can also be entered into the processor ofthe NIBP monitoring system manually.

Once the NIBP monitoring system determines that the patient ispre-eclamptic, either through a prior diagnostic finding or the analysisof the carbon monoxide level within the patient, the processor of theNIBP monitoring system adjusts the blood pressure estimates calculatedby the NIBP monitoring system using its conventional estimationalgorithm. Since the physical characteristics of the blood vesselswithin a pre-eclamptic pregnant patient are different than anormotensive pregnant patient, the physical condition of the bloodvessels effect the blood pressure estimates calculated utilizing thenormal blood pressure estimation techniques. Various different methodsof adjusting the calculated blood pressure estimates from the NIBPmonitoring system are contemplated as being alternative methods forenhancing the operation of the NIBP monitoring system. As an example,fixed offsets may be added to the measured systolic, diastolic and MAPpressure values. Alternatively, offsets that are dependent upon theactual measured systolic, diastolic and MAP pressure values may beutilized. Further, amplitude ratios that are used to determine thesystolic and diastolic pressures from the MAP values may be modifiedwhen the patient is determined to be pre-eclamptic. Further, offsets maybe added to the calculated blood pressure estimate based upon themeasured pulse pressures by the pressure transducer within the bloodpressure cuff. In any case, the blood pressure estimates calculatedutilizing the standard algorithm of the NIBP monitor are modified whenthe patient has been determined to be pre-eclamptic.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated of carryingout the invention. In the drawings:

FIG. 1 is a block diagram of a system for monitoring blood pressureutilizing a non-invasive blood pressure (NIBP) monitor and a carbonmonoxide detection device;

FIG. 2 is a graph depicting the operation of the NIBP monitor todetermine at least the systolic, diastolic and mean arterial pressure ina normal patient;

FIG. 3 is a schematic illustration of the use of a carbon monoxidedetection device along with the NIBP monitor; and

FIG. 4 is a flowchart illustrating the use of the carbon monoxidedetection device with the NIBP monitor to adjust the blood pressureestimates for a patient with pregnancy-induced hypertension orpre-eclampsia.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 generally illustrates a non-invasive blood pressure (NIBP)monitoring system 10 of conventional construction. The NIBP monitoringsystem 10 includes a blood pressure cuff 12 placed on the arm 14 of apatient 16. The blood pressure cuff 12 can be inflated and deflated foroccluding the brachial artery of the patient 16 when in the fullyinflated condition. As the blood pressure cuff 12 is deflated using thedeflate valve 18 having exhaust 20, the arterial occlusion is graduallyrelieved. The deflation of the blood pressure cuff 12 by the deflatevalve 18 is controlled by a central processor 22 through the controlline 24.

A pressure transducer 26 is coupled by duct 28 to the blood pressurecuff 12 for sensing the pressure within the cuff 12. In accordance withconventional oscillometric techniques, the transducer 26 is used tosense pressure oscillations in the cuff 12 that are generated bypressure changes in the brachial artery under the cuff. Thus, thepressure oscillations sensed by the transducer 26 depend upon thephysical characteristics of the brachial artery. The electrical signalsfrom the pressure transducer 26 are obtained by the central processor22, using an analog-to digital converter, through connection line 30.

A source of pressurized air 32 is connected by duct 34 to an inflatevalve 36. The inflate valve 36 is connected by duct 38 to the bloodpressure cuff 12. The operation of the inflate valve 36 is controlled bythe central processor 22 through the control line 24. Thus, theinflation and deflation of the blood pressure cuff 12 is controlled bythe central processor 22 through the deflate valve 18 and the inflatevalve 36, respectively.

From the standpoint of the principles of the present invention, theprocessing of the signals from pressure transducer 26 by the centralprocessor 22 to produce blood pressure data, and optionally to rejectartifact data, can be conducted in accordance with the prior artteachings of the above-referenced Ramsey '029 and '034 patents.Alternatively, the blood pressure can be determined in accordance withthe teachings of Medero et al in U.S. Pat. No. 4,543,962, of Medero inU.S. Pat. No. 4,546,775, of Hood, Jr. et al in U.S. Pat. No. 4,461,266,of Ramsey, III et al in U.S. Pat. No. 4,638,810, of Ramsey III et al inU.S. Pat. No. 4,754,761, of Ramsey III et al in U.S. Pat. No. 5,170,795,of Ramsey III et al in U.S. Pat. No. 5,052,397, of Medero in U.S. Pat.No. 5,577,508 and of Hersh et al in U.S. Pat. No. 5,590,662, all ofwhich are commonly assigned herewith and the disclosures of which arehereby incorporated by reference. In any event, it is desirable to useany of the known techniques to determine the quality of the oscillationcomplexes received at each cuff pressure so that the blood pressuredetermination is made using the physiological relevant cuff pressureoscillations from each heart beat and not artifacts.

During normal operation of the NIBP monitoring system 10 shown in FIG.1, the blood pressure cuff 12 is initially placed on the patient 16,typically around the subject's upper arm 14 over the brachial artery. Atthe inception of the measuring cycle, the blood pressure cuff 12 isinflated to a pressure that fully occludes the brachial artery, i.e.,prevents blood from flowing through the brachial artery at any point inthe heart cycle. In FIG. 2, the initial inflation pressure isillustrated by reference number 40.

After the blood pressure cuff has been inflated to the initial inflationpressure 40, the deflate valve is actuated by the central processor todeflate the cuff in a series of pressure steps 42. Although variousvalues for each pressure step 42 can be utilized, in one embodiment ofthe invention, the pressure step 42 is about 8 mm Hg per step.

After each pressure step 42, the NIBP monitoring system detects andrecords one or more pressure oscillations 44 for the current cuffpressure level. The pressure transducer measures the internal cuffpressure and provides an analog signal characterizing the blood pressureoscillatory complexes. The peak values of the complex signals aredetermined within the central processor.

As the measurement cycles progress, the peak amplitude of the bloodpressure complexes generally become monotonically larger to a maximumand then become monotonically smaller as the cuff pressure continuestoward full deflation, as illustrated by the bell-shaped graph 45 inFIG. 2. The peak amplitude of the cuff pressure oscillation complexes,and the corresponding occluding-cuff pressure values, are retained inthe central processor memory. The oscillometric measurements are used byan algorithm in the central processor to calculate the mean arterialpressure (MAP) 46, the systolic pressure 48 and the diastolic pressure50 in a known manner.

In typical NIBP monitoring systems that utilized the detected pressureoscillations 44 to calculate the systolic pressure 48 and the diastolicpressure 50, these blood pressure estimates are based upon the maximumamplitude of the pressure oscillations, which signify the mean arterialpressure 46. Once the mean arterial pressure 46 has been calculated, thesystolic pressure is typically estimated as a ratio of the MAP 46. As anexample, the systolic pressure 48 is determined to be the cuff pressureat the detected pressure oscillation having an amplitude of ½ themaximum pressure oscillation. Likewise, the diastolic pressure 50 is setto be the cuff pressure past the peak oscillation at which the amplitudeof the pressure oscillation is ⅝ the value of the maximum pressureoscillation. The use of these two ratios to estimate the systolic anddiastolic pressure based upon the detected MAP provides very accurateblood pressure estimations for normotensive patients.

In the normal operation of an NIBP monitor using oscillometric methodsof measuring the blood pressure, the pressure transducer 26 receivessignals from the blood pressure cuff that are, in part, based upon thephysical characteristics of the arteries within the patient beingmonitored. The blood vessels within the patient function as a pressuresensor in transferring pressure pulses that relate to the blood pressurein the patient. If the physical characteristics of the blood vesselswithin the patient are altered, such as during pre-eclampsia, thepressure pulses detected by the pressure transducer are altered ascompared to those from a normotensive patient. Since the physicalcharacteristics of the patient's blood vessels change duringpre-eclampsia, the normal algorithm used to estimate the systolic anddiastolic blood pressures may be inaccurate. Typically, the bloodpressure estimates determined utilizing the typical algorithm from anNIBP monitor result in systolic and diastolic blood pressure estimatesthat are slightly lower than the systolic and diastolic blood pressuremeasurements made by a physician utilizing manual measurement technique,such as with a blood pressure cuff and stethoscope. Since physicianstypically treat patients based upon these manual measurements, the useof the typical NIBP monitoring algorithm may result in lower bloodpressure estimates, thus causing an altered course of treatment.

Referring now to FIG. 1, the monitoring system of the present inventionutilizes a carbon monoxide detection device 52 to detect the level ofcarbon monoxide within the patient's bloodstream as an indication ofpre-eclampsia. In the embodiment shown in FIG. 1, the carbon monoxidedetection device 52 can be one of several different, alternate devicesutilized to detect the level of carbon monoxide within the patient. Thefirst proposed carbon monoxide detection device utilizes a patient mask54 to receive expired gases from the patient. The expired gases receivedby the patient mask 54 are analyzed by the carbon monoxide detectiondevice 52 and an end tidal breath CO (etCO) level is delivered to thecentral processor 22 of the NIBP monitoring system 10 along the controlline 56. Once the central processor 22 receives the etCO level from thecarbon monoxide detection device 52, the central processor 22 cancompare the etCO level to pre-selected limits to determine whether thepatient 16 is pre-eclamptic. Alternatively, the CO detection device 52can include internal software to determine whether the patient ispre-eclamptic and deliver this information to the processor 22.

In addition to utilizing a carbon monoxide detection device thatreceives the expired gases from the patient, the carbon monoxidedetection device 52 could also be a pulse CO-oximetry device thatutilizes a finger probe 58 to estimate the level of carbon monoxide inthe patient's blood. Specifically, the carbon monoxide detection device52 that utilizes the finger probe 58 estimates the carboxyhemoglobin(COHb) level within the patient non-invasively utilizing a modifiedpulse oximeter, such as the RAD-57 Pulse CO Oximeter available fromMassimo. In this type of system, the carbon monoxide detection device 52generates a signal along the control line 56 indicating the COHb levelwithin the patient 16. Upon receiving the COHb level, the centralprocessor 22 can determine whether the patient 16 is pre-eclamptic.Alternatively, the CO detection device 52 can include internal softwareto determine whether the patient is pre-eclamptic and deliver thisinformation to the processor 22.

Although two different alternate types of carbon monoxide detectiondevices 52 are described above as being proposed alternatives, it shouldbe understood that various other alternate carbon monoxide detectiondevices 52 are contemplated as being within the scope of the presentinvention. Additionally, although the carbon monoxide detection device52 is shown separate from the central processor 22, it is contemplatedthat the functionality of the carbon monoxide detection device 52 couldbe incorporated within the NIBP monitoring system 10 such that theinputs from either the patient mask 54 or the finger probe 58 could bedirectly received by the central processor 22, rather than requiring theintermediate carbon monoxide detection device 52.

Referring now to FIG. 3, the NIBP monitoring system 10 is shownconnected to the carbon monoxide detection device 52 to receiveinformation relating to the carbon monoxide levels within the patient16. In this manner, the NIBP monitoring system 10 can determine whetherthe patient is pre-eclamptic, as described above. In addition, the NIBPmonitor 10 is shown connected to an electronic medical records database60 through a control line 62, which may be a hardwire connection or awireless network connection. In this manner, the NIBP monitoring system10 can communicate with the electronic medical records database 60 toreceive information relating to the patient 16. For example, the NIBPmonitoring system 10 can receive information indicating that the patient16 is pre-eclamptic based upon a prior diagnosis. Although high bloodpressure and reduced levels of carbon monoxide are both indicators ofpre-eclampsia, various other clinical information, such as proteinlevels within the urine, are also indicators of pre-eclampsia within apatient. Thus, if the patient has been diagnosed as pre-eclamptic basedupon other test results, the pre-eclampsia diagnosis can be received bythe NIBP monitoring system 10 from the records database 60.

Alternatively, the NIBP monitor also includes input keys that allow aphysician to manually enter an indication that the patient 16 ispre-eclamptic based upon various other test results. Thus, the NIBPmonitoring system 10 can determine that a patient is pre-eclamptic basedupon either direct measurements from the patient's exhaled breath, amodified pulse oximeter measurement from a finger probe, a diagnosisreceived from an electronic medical records database, or based upon amedical entry from a clinician directly into the NIBP monitor. Althoughthese different alternate methods of receiving a pre-eclamptic diagnosisare contemplated, it should be understood that other alternate methodsare contemplated as being within the scope of the present invention.

Referring now to FIG. 4, the method of operating the NIBP monitoringsystem will now be described. As illustrated in FIG. 4, the first stepin the process is for the NIBP monitoring system to obtain theoscillometric pulses from the patient as the blood pressure cuffpressure is stepped down from the initial inflation pressure to a finalinflation pressure, as indicated in step 64. Once the oscillometricpulses have been received from the patient, the processor of the NIBPmonitor can then calculate the typical blood pressure estimates in step66 using its conventional algorithm. As indicated previously, theconventional algorithm utilized in many NIBP monitoring systemsdetermines the systolic and diastolic pressure based upon a ratio of themaximum oscillation amplitude that corresponds to the mean arterialpressure.

Once the processor of the NIBP monitoring system has calculated theblood pressure estimates in step 66, the processor then determines instep 68 whether the patient is pre-eclamptic or suffering frompregnancy-induced hypertension. As described previously, the processorcan make this determination based upon either a signal from a carbonmonoxide detection device, a previous diagnosis received from anelectronic medical records database, or based upon a manual entry madeby the physician into the NIBP monitoring system. In each case, theprocessor of the NIBP monitor must determine whether the patient ispre-eclamptic in step 68 and then modifies the normal blood pressureestimates based upon the determination.

If the processor determines in step 68 that the patient is notpre-eclamptic, the processor displays the blood pressure estimatescalculated in step 66 on the monitor display 72 shown in FIG. 3. Oncethe blood pressure estimates have been displayed in step 70, the systemreturns to step 64 to again obtain the oscillometric pulses from thepatients on a regular interval. As an example, the oscillometric pulsesfrom the patient may be obtained every fifteen minutes or at intervalsdetermined by the physician.

If, however, the processor determines in step 68 that the patient ispre-eclamptic, the system then adjusts the blood pressure estimates instep 74. As described previously, when a patient is pre-eclamptic, theblood pressure estimates determined in step 66 are often low for boththe systolic and diastolic pressure estimates as compared to the bloodpressure manually determined by a physician using a blood pressure cuffand a stethoscope. In accordance with the present invention, theprocessor adjusts the blood pressure estimates in step 74 such that theblood pressure estimates more accurately correspond to manual bloodpressure measurements typically taken by a physician utilizing amanually inflatable blood pressure cuff and stethoscope.

Various different methods are contemplated as being within the scope ofthe present invention to adjust the blood pressure estimate in step 74.Several presently contemplated methods are set forth below asillustrative examples but are not meant to provide an exhaustive listingof all the different types of methods that could be contemplated asbeing within the scope of the present invention.

A first contemplated method of adjusting the blood pressure estimates isto add a fixed offset to the estimated systolic, diastolic and MAPpressure values. The fixed offsets can be determined utilizing historicdata values comparing the blood pressure estimates generated by the NIBPmonitoring system on pre-eclamptic patients as compared to the manualblood pressure values determined by a physician utilizing a manuallyinflatable blood pressure cuff and stethoscope. Based upon thesehistoric values, fixed offsets can be determined and added to thesystolic, diastolic and MAP pressure values calculated in step 66. Theadjusted blood pressure estimate would then be displayed in step 76.

In a second, alternate method of adjusting the blood pressure estimates,the processor of the NIBP monitoring system can add offsets to thecalculated blood pressure estimates that are dependent upon the value ofthe measured systolic, diastolic and/or MAP pressure values. As anexample, the adjusted systolic pressure may be calculated as 125% of thecalculated systolic pressure estimate from step 66. Likewise, theadjusted diastolic pressure may be selected at 125% of the diastolicblood pressure estimate determined in step 66. In this method ofadjusting the blood pressure estimates, the amount of offset isdependent upon the calculated blood pressure estimates and the amount ofoffset will thus vary depending upon the measured blood pressure fromthe patient. Once again, once the adjusted blood pressure estimates havebeen determined, the adjusted blood pressure estimates are displayed instep 76.

As a third contemplated method of adjusting the blood pressureestimates, the processor of the NIBP monitoring system may adjust theamplitude ratios used to determine the systolic and diastolic pressuresin step 66. As described previously, many NIBP monitoring systemsdetermine the systolic and diastolic pressures based upon a ratio of theamplitude of the maximum oscillation pulse, which corresponds to themean arterial pressure. As an example, many NIBP monitoring systemscalculate the systolic pressure as the cuff pressure at which theamplitude of the measured oscillation pulse is ½ the amplitude of themaximum oscillation pulse. In this contemplated method of adjusting theblood pressure estimates, the standard ratio of ½ utilized to calculatethe systolic pressure from the maximum oscillation amplitude and may bemodified to ⅝. Since the ratio has been increased, the systolic bloodpressure estimate will also be increased. Further, the diastolicpressure is typically determined as the cuff pressure at which theamplitude of the pressure oscillations is ⅝ the maximum amplitude of thepressure oscillations. This ratio will also be increased, such as to11/16, to again adjust the calculated diastolic pressure based upon theamplitudes of the oscillation pulses. Once again, once the adjustedblood pressure estimates are calculated, the adjusted blood pressureestimates are displayed in step 76 such that the physician is presentedonly with the adjusted blood pressure estimates and does not view thecalculated blood pressure estimates determined in step 66.

A fourth alternate method of adjusting the blood pressure estimatesincludes adding offsets to the blood pressure estimates based upon themeasured pulse pressures at the systolic and diastolic values. Since theoscillation pulses are the physical characteristics actually measured bythe NIBP monitoring system, adding an offset to the pulse pressureallows the system to compensate the actual physical measurements takenby the system rather than modify the calculations determined by thesystem. Again, once the adjusted blood pressure estimates arecalculated, the adjusted blood pressure estimates are displayed in step76.

Once the system has displayed the adjusted blood pressure estimates, thesystem returns to the beginning of the cycle to obtain the oscillometricpulses from the patient. Referring back to FIGS. 1 and 3, the use of thecarbon monoxide detection device 52 with the conventional NIBPmonitoring system allows the NIBP monitoring system to make a diagnosisof pre-eclampsia based upon carbon monoxide levels detected in real timefrom the patient. Once the NIBP monitoring system determines that thepatient is pre-eclamptic, the processor within the NIBP monitoringsystem can adjust the algorithm used to calculate at least the systolicand diastolic pressures from the patient such that the NIBP monitoringsystem more accurately displays blood pressure for patients that arepre-eclamptic. It is contemplated that the carbon monoxide detectiondevice can detect the level of carbon monoxide in a patient using one ofmultiple different detection techniques, such as detecting the level ofcarbon monoxide in an exhaled patient breath or detecting the level ofCOHb within a patient's bloodstream, utilizing a finger probe. The useof the carbon monoxide detection device 52 allows the pre-eclampsiadetermination to be made in real time based upon patient parameters thatare obtained in synchronization with the calculation of the patientblood pressure. Once the NIBP monitor determines that the patient ispre-eclamptic, the processor within the NIBP monitoring system canadjust its algorithm to more accurately provide an indication of thepatient's blood pressure.

1. A system for monitoring and estimating the blood pressure of apregnant patient, the system comprising: a non-invasive blood pressure(NIBP) monitor including a blood pressure cuff positionable on thepatient, the NIBP monitor including a processor operable to receiveoscillation signals from a transducer within the blood pressure cuff andestimate the patient's blood pressure based upon the oscillationsignals; and a carbon monoxide detection device operable to determinethe carbon monoxide level present within the patient, wherein theprocessor modifies the blood pressure estimate based upon the detectedcarbon monoxide level.
 2. The system of claim 1 wherein the carbonmonoxide detection device is a pulse oximeter sensor positionable on thepatient.
 3. The system of claim 1 wherein the carbon monoxide detectingdevice senses the level of carbon monoxide in the patient's exhaledbreath.
 4. The system of claim 1 wherein the processor estimates atleast a systolic pressure and a diastolic pressure based upon thereceived oscillation signals and a predetermined algorithm, wherein theprocessor adjusts the estimated systolic pressure and diastolic pressurewhen the sensed carbon monoxide level indicate the patient ispre-eclamptic.
 5. The system of claim 1 wherein the processor isoperable to determine whether the patient is pre-eclamptic based uponthe detected carbon monoxide level, wherein the processor modifies theblood pressure estimate when the patient is pre-eclamptic.
 6. The systemof claim 5 wherein the processor estimates at least the systolicpressure and the diastolic pressure, wherein the systolic pressure andthe diastolic pressure estimates are increased when the patient ispre-eclamptic.
 7. The system of claim 2 wherein the pulse oximetersensor is operable to detect the carboxyhemoglobin (COHb) level in thepatient's blood.
 8. A method of monitoring blood pressure in a pregnantpatient, the method comprising the steps of: providing a non-invasiveblood pressure (NIBP) monitor operable to estimate the blood pressure ofthe patient and generate at least an estimated systolic pressure and anestimated diastolic pressure; positioning a carbon monoxide detectiondevice on the patient to detect the level of carbon monoxide in thepatient's blood; receiving an indication of the carbon monoxide level inthe blood of the patient at the NIBP monitor; determining whether thepatient is pre-eclamptic based upon the received carbon monoxide level;adjusting the blood pressure estimates of the NIBP monitor to compensatefor the effects of pre-eclampsia; and displaying the adjusted bloodpressure estimates.
 9. The method of claim 8 wherein the carbon dioxidedetection device is a pulse oximeter that detects the carboxyhemoglobin(COHb) level in the patient's blood.
 10. The method of claim 8 whereinthe carbon dioxide detection device detects the level of carbon monoxidein the patient's exhaled breath.
 11. The method of claim 8 wherein thestep of adjusting the blood pressure estimates includes: increasing theestimated systolic pressure by a first offset value when the patient ispre-eclamptic; and increasing the estimated diastolic pressure by asecond offset value when the patient is pre-eclamptic.
 12. The method ofclaim 8 wherein the step of adjusting the blood pressure estimatesincludes: adjusting the ratio of the systolic pressure from an estimatedmean arterial pressure when the patient is pre-eclamptic; and adjustingthe ratio of the diastolic pressure from the estimated mean arterialpressure when the patient is pre-eclamptic.
 13. The method of claim 11wherein the first and second offset values are determined based on theestimated mean arterial pressure.